Interactive compression with multiple units of compression state information

ABSTRACT

There is provided a method of interactive compression using multiple compression state information entries. The method comprises receiving a request for data from a communicating party; retrieving the data; identifying, for use in compressing the data, at least two compression state information entries shared between the parties to the communication; compressing the data with each of the at least two compression state information entries; determining, from the set of compression state information entries, a preferred compression state information entry that provides a greatest compression ratio; and transmitting the data, compressed in accordance with the preferred compression state information entry to the communicating party.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. application Ser. No. 12/131,407 filedJun. 2, 2008, which claims the benefit of U.S. Provisional ApplicationNo. 60/941,613, filed Jun. 1, 2007, the contents of which incorporatedherein in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to interactive compression. Moreparticularly, the present invention relates to interactive compressionwith multiple units of compression state information.

BACKGROUND OF THE INVENTION

In the field of data communication, data is typically compressed so thatthe amount of information being transmitted is reduced. Such datacompression enables less traffic and therefore faster transmission.Compression also reduces storage requirements, which is especiallyimportant in communication to portable or mobile communication deviceswith limited storage capacity. In conventional communication between aserver and a mobile communication device, requested data, such asmessage data, a website, or a digital file, is encoded, or compressed,by the server, and then transmitted. A decoder at the mobilecommunication device decodes the compressed data, and processes itappropriately, such as displaying it to the user.

Side information, defining parameters to be used in the compression anddecompression of transmitted data, can improve compression performance.The choice of parameters and, therefore, the side information thatdefines those parameters, influences the compression ratio achieved bythe compression. Significantly improved compression can be achieved insystems, known as interactive compression systems, that maintain sharedand coherent caches of side information. With the implementation ofgrammar-based compression technologies, such as Yang-Kieffer (YK)universal data compression, the compression parameters, including thegrammar rules and frequency counts, are updated as the compressionalgorithm evolves the grammar associated with the data being compressed.Related data may share some common portion of the grammar. Thus,knowledge of previously communicated data and the data currently beingrequested could be used to improve compression performance, and toprovide interactive compression. However, side information has notpreviously included such knowledge, nor has a method for maintaining andsharing a coherent cache of such knowledge previously been proposed.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way ofexample only, with reference to the attached Figures, wherein:

FIG. 1 is a block diagram of an exemplary embodiment of a mobile device;

FIG. 2 is a block diagram of an exemplary embodiment of a communicationsubsystem component of the mobile device of FIG. 1;

FIG. 3 is an exemplary block diagram of a node of a wireless network;

FIG. 4 is a block diagram illustrating components of a host system inone exemplary configuration for use with the wireless network of FIG. 3and the mobile device of FIG. 1;

FIG. 5 is a schematic view of a mobile communication device and a serverare shown;

FIG. 6 shows a generic hierarchical node index;

FIGS. 6 a and 6 b show hierarchical node indexes for HTTP and emailmessaging communications, respectively;

FIG. 7 is a flowchart outlining a method of communicating compressionstate information for interactive compression;

FIG. 8 is a flowchart outlining a method of synchronizing sideinformation databases within a device and a server;

FIG. 9 is a flowchart outlining a method of determining compressionstate information;

FIG. 10 is a flowchart outlining a method of interactive compressionusing multiple compression state information entries; and

FIG. 11 is a flowchart outlining a method of the interactive compressionof multi-part requested data.

DETAILED DESCRIPTION

Generally, described is a method and system for performing interactivecompression between communicating parties, such as a server and a mobilecommunication device. In an embodiment, the interactive data compressionis performed using a lossless data compression, such as that describedin U.S. Pat. No. 6,801,141 to Yang et al., which is hereby incorporatedby reference. This type of data compression, using grammar transforms,or rules, is also known as Yang-Kieffer (YK) data compression. In YKdata compression, data is compressed into an irreduciblecontext-dependent grammar form from which the original data may berecovered. The grammar form of previously compressed data can be used incompression of related data, particularly when dealing with data havingsimilar properties and/or content. This grammar form can be used forsubsequent compressions by storing parameters, such as the actualgrammar rules and frequency counts, as compression state information,and can result in much enhanced compression, particularly in terms ofincreased speed of compression and reduced use of processing resources.

It will be appreciated that for simplicity and clarity of illustration,where considered appropriate, reference numerals may be repeated amongthe figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein may be practiced without these specificdetails. In other instances, well-known methods, procedures andcomponents have not been described in detail so as not to obscure theembodiments described herein. Also, the description is not to beconsidered as limiting the scope of the embodiments described herein.

The embodiments described herein generally relate to a mobile wirelesscommunication device, hereafter referred to as a mobile device. Examplesof applicable communication devices include pagers, cellular phones,cellular smart-phones, wireless organizers, personal digital assistants,computers, laptops, handheld wireless communication devices, wirelesslyenabled notebook computers and the like.

The mobile device is a two-way communication device with advanced datacommunication capabilities including the capability to communicate withother mobile devices or computer systems through a network oftransceiver stations. The mobile device may also have the capability toallow voice communication. Depending on the functionality provided bythe mobile device, it may be referred to as a data messaging device, atwo-way pager, a cellular telephone with data messaging capabilities, awireless Internet appliance, or a data communication device (with orwithout telephony capabilities). To aid the reader in understanding thestructure of the mobile device and how it communicates with otherdevices and host systems, reference will now be made to FIGS. 1 through4.

Referring first to FIG. 1, shown therein is a block diagram of anexemplary embodiment of a mobile device 100. The mobile device 100includes a number of components such as a main processor 102 thatcontrols the overall operation of the mobile device 100. Communicationfunctions, including data and voice communications, are performedthrough a communication subsystem 104. Data received by the mobiledevice 100 can be decompressed and decrypted by decoder 103, operatingaccording to any suitable decompression techniques (e.g. YKdecompression, and other known techniques) and encryption techniques(e.g. using an encryption techniques such as Data Encryption Standard(DES), Triple DES, or Advanced Encryption Standard (AES)). Thecommunication subsystem 104 receives messages from and sends messages toa wireless network 200. In this exemplary embodiment of the mobiledevice 100, the communication subsystem 104 is configured in accordancewith the Global System for Mobile Communication (GSM) and General PacketRadio Services (GPRS) standards. The GSM/GPRS wireless network is usedworldwide and it is expected that these standards will be supersededeventually by Enhanced Data GSM Environment (EDGE) and Universal MobileTelecommunications Service (UMTS). New standards are still beingdefined, but it is believed that they will have similarities to thenetwork behavior described herein, and it will also be understood bypersons skilled in the art that the embodiments described herein areintended to use any other suitable standards that are developed in thefuture. The wireless link connecting the communication subsystem 104with the wireless network 200 represents one or more different RadioFrequency (RF) channels, operating according to defined protocolsspecified for GSM/GPRS communications. With newer network protocols,these channels are capable of supporting both circuit switched voicecommunications and packet switched data communications.

Although the wireless network 200 associated with mobile device 100 is aGSM/GPRS wireless network in one exemplary implementation, otherwireless networks may also be associated with the mobile device 100 invariant implementations. The different types of wireless networks thatmay be employed include, for example, data-centric wireless networks,voice-centric wireless networks, and dual-mode networks that can supportboth voice and data communications over the same physical base stations.Combined dual-mode networks include, but are not limited to, CodeDivision Multiple Access (CDMA) or CDMA2000 networks, GSM/GPRS networks(as mentioned above), and future third-generation (3G) networks likeEDGE and UMTS. Some other examples of data-centric networks include WiFi802.11, Mobitex™ and DataTAC™ network communication systems. Examples ofother voice-centric data networks include Personal Communication Systems(PCS) networks like GSM and Time Division Multiple Access (TDMA)systems. The main processor 102 also interacts with additionalsubsystems such as a Random Access Memory (RAM) 106, a flash memory 108,a display 110, an auxiliary input/output (I/O) subsystem 112, a dataport 114, a keyboard 116, a speaker 118, a microphone 120, short-rangecommunications 122 and other device subsystems 124.

Some of the subsystems of the mobile device 100 performcommunication-related functions, whereas other subsystems may provide“resident” or on-device functions. By way of example, the display 110and the keyboard 116 may be used for both communication-relatedfunctions, such as entering a text message for transmission over thenetwork 200, and device-resident functions such as a calculator or tasklist.

The mobile device 100 can send and receive communication signals overthe wireless network 200 after required network registration oractivation procedures have been completed. Network access is associatedwith a subscriber or user of the mobile device 100. To identify asubscriber, the mobile device 100 requires a SIM/RUIM card 126 (i.e.Subscriber Identity Module or a Removable User Identity Module) to beinserted into a SIM/RUIM interface 128 in order to communicate with anetwork. The SIM card or RUIM 126 is one type of a conventional “smartcard” that can be used to identify a subscriber of the mobile device 100and to personalize the mobile device 100, among other things. Withoutthe SIM card 126, the mobile device 100 is not fully operational forcommunication with the wireless network 200. By inserting the SIMcard/RUIM 126 into the SIM/RUIM interface 128, a subscriber can accessall subscribed services. Services may include: web browsing andmessaging such as e-mail, voice mail, Short Message Service (SMS), andMultimedia Messaging Services (MMS). More advanced services may include:point of sale, field service and sales force automation. The SIMcard/RUIM 126 includes a processor and memory for storing information.Once the SIM card/RUIM 126 is inserted into the SIM/RUIM interface 128,it is coupled to the main processor 102. In order to identify thesubscriber, the SIM card/RUIM 126 can include some user parameters suchas an International Mobile Subscriber Identity (IMSI). An advantage ofusing the SIM card/RUIM 126 is that a subscriber is not necessarilybound by any single physical mobile device. The SIM card/RUIM 126 maystore additional subscriber information for a mobile device as well,including datebook (or calendar) information and recent callinformation. Alternatively, user identification information can also beprogrammed into the flash memory 108.

The mobile device 100 is a battery-powered device and includes a batteryinterface 132 for receiving one or more rechargeable batteries 130. Inat least some embodiments, the battery 130 can be a smart battery withan embedded microprocessor. The battery interface 132 is coupled to aregulator (not shown), which assists the battery 130 in providing powerV+ to the mobile device 100. Although current technology makes use of abattery, future technologies such as micro fuel cells may provide thepower to the mobile device 100.

The mobile device 100 also includes an operating system 134 and softwarecomponents 136 to 146 which are described in more detail below. Theoperating system 134 and the software components 136 to 146 that areexecuted by the main processor 102 are typically stored in a persistentstore such as the flash memory 108, which may alternatively be aread-only memory (ROM) or similar storage element (not shown). Thoseskilled in the art will appreciate that portions of the operating system134 and the software components 136 to 146, such as specific deviceapplications, or parts thereof, may be temporarily loaded into avolatile store such as the RAM 106. Other software components can alsobe included, as is well known to those skilled in the art.

The subset of software applications 136 that control basic deviceoperations, including data and voice communication applications, willnormally be installed on the mobile device 100 during its manufacture.Other software applications include a message application 138 that canbe any suitable software program that allows a user of the mobile device100 to send and receive electronic messages. Various alternatives existfor the message application 138 as is well known to those skilled in theart. Messages that have been sent or received by the user are typicallystored in the flash memory 108 of the mobile device 100 or some othersuitable storage element in the mobile device 100. In at least someembodiments, some of the sent and received messages may be storedremotely from the device 100 such as in a data store of an associatedhost system that the mobile device 100 communicates with.

The software applications can further include a device state module 140,a Personal Information Manager (PIM) 142, and other suitable modules(not shown). The device state module 140 provides persistence, i.e. thedevice state module 140 ensures that important device data is stored inpersistent memory, such as the flash memory 108, so that the data is notlost when the mobile device 100 is turned off or loses power.

The PIM 142 includes functionality for organizing and managing dataitems of interest to the user, such as, but not limited to, e-mail,contacts, calendar events, voice mails, appointments, and task items. APIM application has the ability to send and receive data items via thewireless network 200. PIM data items may be seamlessly integrated,synchronized, and updated via the wireless network 200 with the mobiledevice subscriber's corresponding data items stored and/or associatedwith a host computer system. This functionality creates a mirrored hostcomputer on the mobile device 100 with respect to such items. This canbe particularly advantageous when the host computer system is the mobiledevice subscriber's office computer system.

The mobile device 100 also includes a connect module 144, and aninformation technology (IT) policy module 146. The connect module 144implements the communication protocols that are required for the mobiledevice 100 to communicate with the wireless infrastructure and any hostsystem, such as an enterprise system, that the mobile device 100 isauthorized to interface with. Examples of a wireless infrastructure andan enterprise system are given in FIGS. 3 and 4, which are described inmore detail below.

The connect module 144 includes a set of APIs that can be integratedwith the mobile device 100 to allow the mobile device 100 to use anynumber of services associated with the enterprise system. The connectmodule 144 allows the mobile device 100 to establish an end-to-endsecure, authenticated communication pipe with the host system. A subsetof applications for which access is provided by the connect module 144can be used to pass IT policy commands from the host system to themobile device 100. This can be done in a wireless or wired manner. Theseinstructions can then be passed to the IT policy module 146 to modifythe configuration of the device 100. Alternatively, in some cases, theIT policy update can also be done over a wired connection.

Other types of software applications can also be installed on the mobiledevice 100. These software applications can be third party applications,which are added after the manufacture of the mobile device 100. Examplesof third party applications include games, calculators, utilities, etc.

The additional applications can be loaded onto the mobile device 100through at least one of the wireless network 200, the auxiliary I/Osubsystem 112, the data port 114, the short-range communicationssubsystem 122, or any other suitable device subsystem 124. Thisflexibility in application installation increases the functionality ofthe mobile device 100 and may provide enhanced on-device functions,communication-related functions, or both. For example, securecommunication applications may enable electronic commerce functions andother such financial transactions to be performed using the mobiledevice 100.

The data port 114 enables a subscriber to set preferences through anexternal device or software application and extends the capabilities ofthe mobile device 100 by providing for information or software downloadsto the mobile device 100 other than through a wireless communicationnetwork. The alternate download path may, for example, be used to loadan encryption key onto the mobile device 100 through a direct and thusreliable and trusted connection to provide secure device communication.

The data port 114 can be any suitable port that enables datacommunication between the mobile device 100 and another computingdevice. The data port 114 can be a serial or a parallel port. In someinstances, the data port 114 can be a USB port that includes data linesfor data transfer and a supply line that can provide a charging currentto charge the battery 130 of the mobile device 100.

The short-range communications subsystem 122 provides for communicationbetween the mobile device 100 and different systems or devices, withoutthe use of the wireless network 200. For example, the subsystem 122 mayinclude an infrared device and associated circuits and components forshort-range communication. Examples of short-range communicationstandards include standards developed by the Infrared Data Association(IrDA), Bluetooth, and the 802.11 family of standards developed by IEEE.

In use, a received signal such as a text message, an e-mail message, orweb page download will be processed by the communication subsystem 104and input to the main processor 102. The main processor 102 will thenprocess the received signal for output to the display 110 oralternatively to the auxiliary I/O subsystem 112. A subscriber may alsocompose data items, such as e-mail messages, for example, using thekeyboard 116 in conjunction with the display 110 and possibly theauxiliary I/O subsystem 112. The auxiliary subsystem 112 may includedevices such as: a touch screen, mouse, track ball, infrared fingerprintdetector, or a roller wheel with dynamic button pressing capability. Thekeyboard 116 is preferably an alphanumeric keyboard and/ortelephone-type keypad. However, other types of keyboards may also beused. A composed item may be transmitted over the wireless network 200through the communication subsystem 104.

For voice communications, the overall operation of the mobile device 100is substantially similar, except that the received signals are output tothe speaker 118, and signals for transmission are generated by themicrophone 120. Alternative voice or audio I/O subsystems, such as avoice message recording subsystem, can also be implemented on the mobiledevice 100. Although voice or audio signal output is accomplishedprimarily through the speaker 118, the display 110 can also be used toprovide additional information such as the identity of a calling party,duration of a voice call, or other voice call related information.

Referring now to FIG. 2, an exemplary block diagram of the communicationsubsystem component 104 is shown. The communication subsystem 104includes a receiver 150, a transmitter 152, as well as associatedcomponents such as one or more embedded or internal antenna elements 154and 156, Local Oscillators (LOs) 158, and a processing module such as aDigital Signal Processor (DSP) 160. The particular design of thecommunication subsystem 104 is dependent upon the communication network200 with which the mobile device 100 is intended to operate. Thus, itshould be understood that the design illustrated in FIG. 2 serves onlyas one example.

Signals received by the antenna 154 through the wireless network 200 areinput to the receiver 150, which may perform such common receiverfunctions as signal amplification, frequency down conversion, filtering,channel selection, and analog-to-digital (A/D) conversion. ND conversionof a received signal allows more complex communication functions such asdemodulation and decoding to be performed in the DSP 160. In a similarmanner, signals to be transmitted are processed, including modulationand encoding, by the DSP 160. These DSP-processed signals are input tothe transmitter 152 for digital-to-analog (D/A) conversion, frequency upconversion, filtering, amplification and transmission over the wirelessnetwork 200 via the antenna 156. The DSP 160 not only processescommunication signals, but also provides for receiver and transmittercontrol. For example, the gains applied to communication signals in thereceiver 150 and the transmitter 152 may be adaptively controlledthrough automatic gain control algorithms implemented in the DSP 160.

The wireless link between the mobile device 100 and the wireless network200 can contain one or more different channels, typically different RFchannels, and associated protocols used between the mobile device 100and the wireless network 200. An RF channel is a limited resource thatshould be conserved, typically due to limits in overall bandwidth andlimited battery power of the mobile device 100.

When the mobile device 100 is fully operational, the transmitter 152 istypically keyed or turned on only when it is transmitting to thewireless network 200 and is otherwise turned off to conserve resources.Similarly, the receiver 150 is periodically turned off to conserve poweruntil it is needed to receive signals or information (if at all) duringdesignated time periods.

Referring now to FIG. 3, a block diagram of an exemplary implementationof a node 202 of the wireless network 200 is shown. In practice, thewireless network 200 comprises one or more nodes 202. In conjunctionwith the connect module 144, the mobile device 100 can communicate withthe node 202 within the wireless network 200. In the exemplaryimplementation of FIG. 3, the node 202 is configured in accordance withGeneral Packet Radio Service (GPRS) and Global Systems for Mobile (GSM)technologies. The node 202 includes a base station controller (BSC) 204with an associated tower station 206, a Packet Control Unit (PCU) 208added for GPRS support in GSM, a Mobile Switching Center (MSC) 210, aHome Location Register (HLR) 212, a Visitor Location Registry (VLR) 214,a Serving GPRS Support Node (SGSN) 216, a Gateway GPRS Support Node(GGSN) 218, and a Dynamic Host Configuration Protocol (DHCP) 220. Thislist of components is not meant to be an exhaustive list of thecomponents of every node 202 within a GSM/GPRS network, but rather alist of components that are commonly used in communications through thenetwork 200.

In a GSM network, the MSC 210 is coupled to the BSC 204 and to alandline network, such as a Public Switched Telephone Network (PSTN) 222to satisfy circuit switched requirements. The connection through the PCU208, the SGSN 216 and the GGSN 218 to a public or private network(Internet) 224 (also referred to herein generally as a shared networkinfrastructure) represents the data path for GPRS capable mobiledevices. In a GSM network extended with GPRS capabilities, the BSC 204also contains the Packet Control Unit (PCU) 208 that connects to theSGSN 216 to control segmentation, radio channel allocation and tosatisfy packet switched requirements. To track the location of themobile device 100 and availability for both circuit switched and packetswitched management, the HLR 212 is shared between the MSC 210 and theSGSN 216. Access to the VLR 214 is controlled by the MSC 210.

The station 206 is a fixed transceiver station and together with the BSC204 form fixed transceiver equipment. The fixed transceiver equipmentprovides wireless network coverage for a particular coverage areacommonly referred to as a “cell”. The fixed transceiver equipmenttransmits communication signals to and receives communication signalsfrom mobile devices within its cell via the station 206. The fixedtransceiver equipment normally performs such functions as modulation andpossibly encoding and/or encryption of signals to be transmitted to themobile device 100 in accordance with particular, usually predetermined,communication protocols and parameters, under control of its controller.The fixed transceiver equipment similarly demodulates and possiblydecodes and decrypts, if necessary, any communication signals receivedfrom the mobile device 100 within its cell. Communication protocols andparameters may vary between different nodes. For example, one node mayemploy a different modulation scheme and operate at differentfrequencies than other nodes.

For all mobile devices 100 registered with a specific network, permanentconfiguration data such as a user profile is stored in the HLR 212. TheHLR 212 also contains location information for each registered mobiledevice and can be queried to determine the current location of a mobiledevice. The MSC 210 is responsible for a group of location areas andstores the data of the mobile devices currently in its area ofresponsibility in the VLR 214. Further, the VLR 214 also containsinformation on mobile devices that are visiting other networks. Theinformation in the VLR 214 includes part of the permanent mobile devicedata transmitted from the HLR 212 to the VLR 214 for faster access. Bymoving additional information from a remote HLR 212 node to the VLR 214,the amount of traffic between these nodes can be reduced so that voiceand data services can be provided with faster response times and at thesame time requiring less use of computing resources.

The SGSN 216 and the GGSN 218 are elements added for GPRS support;namely packet switched data support, within GSM. The SGSN 216 and theMSC 210 have similar responsibilities within the wireless network 200 bykeeping track of the location of each mobile device 100. The SGSN 216also performs security functions and access control for data traffic onthe wireless network 200. The GGSN 218 provides internetworkingconnections with external packet switched networks and connects to oneor more SGSN's 216 via an Internet Protocol (IP) backbone networkoperated within the network 200. During normal operations, a givenmobile device 100 must perform a “GPRS Attach” to acquire an IP addressand to access data services. This requirement is not present in circuitswitched voice channels as Integrated Services Digital Network (ISDN)addresses are used for routing incoming and outgoing calls. Currently,all GPRS capable networks use private, dynamically assigned IPaddresses, thus requiring the DHCP server 220 connected to the GGSN 218.There are many mechanisms for dynamic IP assignment, including using acombination of a Remote Authentication Dial-In User Service (RADIUS)server and a DHCP server. Once the GPRS Attach is complete, a logicalconnection is established from a mobile device 100, through the PCU 208,and the SGSN 216 to an Access Point Node (APN) within the GGSN 218. TheAPN represents a logical end of an IP tunnel that can either accessdirect Internet compatible services or private network connections. TheAPN also represents a security mechanism for the network 200, insofar aseach mobile device 100 must be assigned to one or more APNs and mobiledevices 100 cannot exchange data without first performing a GPRS Attachto an APN that it has been authorized to use. The APN may be consideredto be similar to an Internet domain name such as“myconnection.wireless.com”.

Once the GPRS Attach operation is complete, a tunnel is created and alltraffic is exchanged within standard IP packets using any protocol thatcan be supported in IP packets. This includes tunneling methods such asIP over IP as in the case with some IPSecurity (IPsec) connections usedwith Virtual Private Networks (VPN). These tunnels are also referred toas Packet Data Protocol (PDP) Contexts and there are a limited number ofthese available in the network 200. To maximize use of the PDP Contexts,the network 200 will run an idle timer for each PDP Context to determineif there is a lack of activity. When a mobile device 100 is not usingits PDP Context, the PDP Context can be de-allocated and the IP addressreturned to the IP address pool managed by the DHCP server 220.

Referring now to FIG. 4, shown therein is a block diagram illustratingcomponents of an exemplary configuration of a host system 250 that themobile device 100 can communicate with in conjunction with the connectmodule 144. The host system 250 will typically be a corporate enterpriseor other local area network (LAN), but may also be a home officecomputer or some other private system, for example, in variantimplementations. In this example shown in FIG. 4, the host system 250 isdepicted as a LAN of an organization to which a user of the mobiledevice 100 belongs. Typically, a plurality of mobile devices cancommunicate wirelessly with the host system 250 through one or morenodes 202 of the wireless network 200.

The host system 250 comprises a number of network components connectedto each other by a network 260. For instance, a user's desktop computer262 a with an accompanying cradle 264 for the user's mobile device 100is situated on a LAN connection. The cradle 264 for the mobile device100 can be coupled to the computer 262 a by a serial or a UniversalSerial Bus (USB) connection, for example. Other user computers 262 b-262n are also situated on the network 260, and each may or may not beequipped with an accompanying cradle 264. The cradle 264 facilitates theloading of information (e.g. PIM data, private symmetric encryption keysto facilitate secure communications) from the user computer 262 a to themobile device 100, and may be particularly useful for bulk informationupdates often performed in initializing the mobile device 100 for use.The information downloaded to the mobile device 100 may includecertificates used in the exchange of messages.

It will be understood by persons skilled in the art that the usercomputers 262 a-262 n will typically also be connected to otherperipheral devices, such as printers, etc. which are not explicitlyshown in FIG. 4. Furthermore, only a subset of network components of thehost system 250 are shown in FIG. 4 for ease of exposition, and it willbe understood by persons skilled in the art that the host system 250will comprise additional components that are not explicitly shown inFIG. 4 for this exemplary configuration. More generally, the host system250 may represent a smaller part of a larger network (not shown) of theorganization, and may comprise different components and/or be arrangedin different topologies than that shown in the exemplary embodiment ofFIG. 4.

To facilitate the operation of the mobile device 100 and the wirelesscommunication of messages and message-related data between the mobiledevice 100 and components of the host system 250, a number of wirelesscommunication support components 270 can be provided. In someimplementations, the wireless communication support components 270 caninclude a message management server 272, a mobile data server (MDS) 274,a web server, such as Hypertext Transfer Protocol (HTTP) server 275, acontact server 276, and a device manager module 278. HTTP servers canalso be located outside the enterprise system, as indicated by the HTTPserver 275 attached to the network 224. The device manager module 278includes an IT Policy editor 280 and an IT user property editor 282, aswell as other software components for allowing an IT administrator toconfigure the mobile devices 100. In an alternative embodiment, theremay be one editor that provides the functionality of both the IT policyeditor 280 and the IT user property editor 282. The support components270 also include a data store 284, and an IT policy server 286. The ITpolicy server 286 includes a processor 288, a network interface 290 anda memory unit 292. The processor 288 controls the operation of the ITpolicy server 286 and executes functions related to the standardized ITpolicy as described below. The network interface 290 allows the ITpolicy server 286 to communicate with the various components of the hostsystem 250 and the mobile devices 100. The memory unit 292 can storefunctions used in implementing the IT policy as well as related data.Those skilled in the art know how to implement these various components.Other components may also be included as is well known to those skilledin the art. Further, in some implementations, the data store 284 can bepart of any one of the servers.

In this exemplary embodiment, the mobile device 100 communicates withthe host system 250 through node 202 of the wireless network 200 and ashared network infrastructure 224 such as a service provider network orthe public Internet. Access to the host system 250 may be providedthrough one or more routers (not shown), and computing devices of thehost system 250 may operate from behind a firewall or proxy server 266.The proxy server 266 provides a secure node and a wireless internetgateway for the host system 250. The proxy server 266 intelligentlyroutes data to the correct destination server within the host system250.

In some implementations, the host system 250 can include a wireless VPNrouter (not shown) to facilitate data exchange between the host system250 and the mobile device 100. The wireless VPN router allows a VPNconnection to be established directly through a specific wirelessnetwork to the mobile device 100. The wireless VPN router can be usedwith the Internet Protocol (IP) Version 6 (IPV6) and IP-based wirelessnetworks. This protocol can provide enough IP addresses so that eachmobile device has a dedicated IP address, making it possible to pushinformation to a mobile device at any time. An advantage of using awireless VPN router is that it can be an off-the-shelf VPN component,and does not require a separate wireless gateway and separate wirelessinfrastructure. A VPN connection can preferably be a TransmissionControl Protocol (TCP)/IP or User Datagram Protocol (UDP)/IP connectionfor delivering the messages directly to the mobile device 100 in thisalternative implementation.

Messages intended for a user of the mobile device 100 are initiallyreceived by a message server 268 of the host system 250. Such messagesmay originate from any number of sources. For instance, a message mayhave been sent by a sender from the computer 262 b within the hostsystem 250, from a different mobile device (not shown) connected to thewireless network 200 or a different wireless network, or from adifferent computing device, or other device capable of sending messages,via the shared network infrastructure 224, possibly through anapplication service provider (ASP) or Internet service provider (ISP),for example.

The message server 268 typically acts as the primary interface for theexchange of messages, particularly e-mail messages, within theorganization and over the shared network infrastructure 224. Each userin the organization that has been set up to send and receive messages istypically associated with a user account managed by the message server268. Some exemplary implementations of the message server 268 include aMicrosoft Exchange™ server, a Lotus Domino™ server, a Novell Groupwise™server, or another suitable mail server installed in a corporateenvironment. In some implementations, the host system 250 may comprisemultiple message servers 268. The message server 268 may also be adaptedto provide additional functions beyond message management, including themanagement of data associated with calendars and task lists, forexample.

When messages are received by the message server 268, they are typicallystored in a data store associated with the message server 268. In atleast some embodiments, the data store may be a separate hardware unit,such as data store 284, that the message server 268 communicates with.Messages can be subsequently retrieved and delivered to users byaccessing the message server 268. For instance, an e-mail clientapplication operating on a user's computer 262 a may request the e-mailmessages associated with that user's account stored on the data storeassociated with the message server 268. These messages are thenretrieved from the data store and stored locally on the computer 262 a.The data store associated with the message server 268 can store copiesof each message that is locally stored on the mobile device 100.Alternatively, the data store associated with the message server 268 canstore all of the messages for the user of the mobile device 100 and onlya smaller number of messages can be stored on the mobile device 100 toconserve memory. For instance, the most recent messages (i.e. thosereceived in the past two to three months for example) can be stored onthe mobile device 100.

When operating the mobile device 100, the user may wish to have e-mailmessages retrieved for delivery to the mobile device 100. The messageapplication 138 operating on the mobile device 100 may also requestmessages associated with the user's account from the message server 268.The message application 138 may be configured (either by the user or byan administrator, possibly in accordance with an organization's ITpolicy) to make this request at the direction of the user, at somepre-defined time interval, or upon the occurrence of some pre-definedevent. In some implementations, the mobile device 100 is assigned itsown e-mail address, and messages addressed specifically to the mobiledevice 100 are automatically redirected to the mobile device 100 as theyare received by the message server 268.

The message management server 272 can be used to specifically providesupport for the management of messages, such as e-mail messages, thatare to be handled by mobile devices. Generally, while messages are stillstored on the message server 268, the message management server 272 canbe used to control when, if, and how messages are sent to the mobiledevice 100. The message management server 272 also facilitates thehandling of messages composed on the mobile device 100, which are sentto the message server 268 for subsequent delivery.

For example, the message management server 272 may monitor the user's“mailbox” (e.g. the message store associated with the user's account onthe message server 268) for new e-mail messages, and applyuser-definable filters to new messages to determine if and how themessages are relayed to the user's mobile device 100. The messagemanagement server 272 may also, through an encoder 273, compressmessages, using any suitable compression technology (e.g. YKcompression, and other known techniques) and encrypt messages (e.g.using an encryption technique such as Data Encryption Standard (DES),Triple DES, or Advanced Encryption Standard (AES)), and push them to themobile device 100 via the shared network infrastructure 224 and thewireless network 200. The message management server 272 may also receivemessages composed on the mobile device 100 (e.g. encrypted using TripleDES), decrypt and decompress the composed messages, re-format thecomposed messages if desired so that they will appear to have originatedfrom the user's computer 262 a, and re-route the composed messages tothe message server 268 for delivery.

Certain properties or restrictions associated with messages that are tobe sent from and/or received by the mobile device 100 can be defined(e.g. by an administrator in accordance with IT policy) and enforced bythe message management server 272. These may include whether the mobiledevice 100 may receive encrypted and/or signed messages, minimumencryption key sizes, whether outgoing messages must be encrypted and/orsigned, and whether copies of all secure messages sent from the mobiledevice 100 are to be sent to a pre-defined copy address, for example.

The message management server 272 may also be adapted to provide othercontrol functions, such as only pushing certain message information orpre-defined portions (e.g. “blocks”) of a message stored on the messageserver 268 to the mobile device 100. For example, in some cases, when amessage is initially retrieved by the mobile device 100 from the messageserver 268, the message management server 272 may push only the firstpart of a message to the mobile device 100, with the part being of apre-defined size (e.g. 2 KB). The user can then request that more of themessage be delivered in similar-sized blocks by the message managementserver 272 to the mobile device 100, possibly up to a maximumpre-defined message size. Accordingly, the message management server 272facilitates better control over the type of data and the amount of datathat is communicated to the mobile device 100, and can help to minimizepotential waste of bandwidth or other resources.

The MDS 274 encompasses any other server that stores information that isrelevant to the corporation. The mobile data server 274 may include, butis not limited to, databases, online data document repositories,customer relationship management (CRM) systems, or enterprise resourceplanning (ERP) applications. The MDS 274 can also connect to theInternet or other public network, through HTTP server 275 or othersuitable web server such as an File Transfer Protocol (FTP) server, toretrieve HTTP webpages and other data. Requests for webpages aretypically routed through MDS 274 and then to HTTP server 275, throughsuitable firewalls and other protective mechanisms. The web server thenretrieves the webpage over the Internet, and returns it to MDS 274. Asdescribed above in relation to message management server 272, MDS 274 istypically provided, or associated, with an encoder 277 that permitsretrieved data, such as retrieved webpages, to be compressed, using anysuitable compression technology (e.g. YK compression, and other knowntechniques), and encrypted (e.g. using an encryption technique such asDES, Triple DES, or AES), and then pushed to the mobile device 100 viathe shared network infrastructure 224 and the wireless network 200.

The contact server 276 can provide information for a list of contactsfor the user in a similar fashion as the address book on the mobiledevice 100. Accordingly, for a given contact, the contact server 276 caninclude the name, phone number, work address and e-mail address of thecontact, among other information. The contact server 276 can alsoprovide a global address list that contains the contact information forall of the contacts associated with the host system 250.

It will be understood by persons skilled in the art that the messagemanagement server 272, the MDS 274, the HTTP server 275, the contactserver 276, the device manager module 278, the data store 284 and the ITpolicy server 286 do not need to be implemented on separate physicalservers within the host system 250. For example, some or all of thefunctions associated with the message management server 272 may beintegrated with the message server 268, or some other server in the hostsystem 250. Alternatively, the host system 250 may comprise multiplemessage management servers 272, particularly in variant implementationswhere a large number of mobile devices need to be supported.

The device manager module 278 provides an IT administrator with agraphical user interface with which the IT administrator interacts toconfigure various settings for the mobile devices 100. As mentioned, theIT administrator can use IT policy rules to define behaviors of certainapplications on the mobile device 100 that are permitted such as phone,web browser or Instant Messenger use. The IT policy rules can also beused to set specific values for configuration settings that anorganization requires on the mobile devices 100 such as auto signaturetext, WLAN/VoIP/VPN configuration, security requirements (e.g.encryption algorithms, password rules, etc.), specifying themes orapplications that are allowed to run on the mobile device 100, and thelike.

Referring to FIG. 5, a schematic view of the mobile device 100 and aserver, such as MDS 274, the message management server 272 or any otherserver involved in the transfer of information or data to and from themobile device 100, is shown. The mobile device 100 and the server can beseen as communicating parties for a method of interactive compression.

The mobile device 100 includes a main processor 102, a decoder 103, anda device side information database 314, which can also be described as acache, store, or repository. The device side information database 314stores a plurality of units of side information 316. Side information isinformation which is used to describe parameters associated with datasuch as emails or web pages. This side information can includecompression state information 318. The compression state information 318includes parameters, such as grammar rules and/or frequency counts, ofpreviously completed compressions. As previously noted, the compressionstate information from previously completed compressions can improvecompression of subsequent data having similar properties and/or content.The server includes a processor 320, and has access to an encoder, suchas encoder 277, and a server side information database 324. The encoder277 and the server side information database 324 can be integral withthe server, or separate therefrom. The server side information database324 generally contains side information, including compression stateinformation, associated with multiple mobile devices. The server isconnected to the network 200 so that it may retrieve data from otherservers connected to the network, such as HTTP server 275, as isdescribed in more detail below.

The side information stored in the respective side information databases314 and 324 can be organized, or represented, hierarchically, orotherwise mapped or structured for retrieval. The following discussionwill describe the retrieval of side information, including compressionstate information, in a hierarchical trie structure. However, anyrepresentation of data in which side information is searchably mapped,or associated, with its respective originating data, and that can besearched or traversed to determine related nodes or to otherwiseidentify data related to a current compression, can be used. Thestructuring of the side information into a trie structure is a choice ofimplementation.

Interactive compression according to the present invention can begenerally understood by reference to an exemplary HTTP webpagetransmission to the mobile device 100. More specific examples, withreference to FIGS. 6-11 are provided below. The mobile device 100identifies data to request, such as a webpage identified by a UniformResource Locator (URL). The device 100 then parses the URL to determineits constituent elements (e.g. media-type, domain name, path, andoptionally query) that identify, or otherwise point to the location orpath to, the requested data, and searches its device side informationdatabase 314 to identify at least one compression state informationentry that is associated with the nearest related previously compresseddata. The nearest related previously compressed data can be identifiedby comparison of the constituent elements of the requested data to thedata representation stored in the device side information database 314.For example, at a minimum, the nearest related previously compresseddata and currently requested data should have the same media-type, andshould share a minimum number of common elements. While the media-typemay not be known until a valid response is received, the device 100 canassume that the file extension (e.g. “exe”, “txt”, “html”, “gif”, etc)is a good indication of the media type of the response. The minimumnumber of common elements can be a certain number of constituentelements from the URL, such as the domain name and a specified number ofpath elements. If multiple compression state information entries areidentified, rules can be used to preferentially select those that weremost recently created. An identification of one, or more, of theidentified compression state information entries is then appended to theHTTP request header and sent with the data request to the server. Thisidentification can include one or more hashes designed to minimize thelikelihood of multiple compression state information entries resolvingto the same index. The server retrieves the requested data, and uses thecompression state information identification to locate the correspondingcompression state information entry. The compression parameters of theencoder 277 are then set according to the identified compression stateinformation, and the requested data is encoded. If, for any reason, theserver cannot use or locate the identified compression stateinformation, the requested data can be encoded using an encoder-selectedcompression state information entry, or with no compression stateinformation (i.e. from scratch). The compressed data is then sent to thedevice 100, with an identification of the state compression information,or the state compression information itself, used in the compression inits HTTP response header. The state compression information thusidentified or transmitted can be used by the decoder 103 to decompressand display the requested data.

FIGS. 6-11 will now be discussed with reference to FIGS. 1-5. FIG. 6shows a representative hierarchical node index, or tree. Thehierarchical node index is illustrated as a trie structure having aplurality of nodes. A trie structure or, prefix tree, is an ordered treedata structure that is used to store an ordered mapping of nodes thatare generally represented as strings. Each path down the tree, such asthe path 332, has a leaf, or terminating, node, such as node 1.2.2.Every leaf node represents, points to, or otherwise associates to, aunit of side information. In some implementations the other nodes in apath, such as nodes 0, 1 and 1.2, may also each be associated with aunit of side information. Each unit of side information containscompression state information.

There are a variety of ways in which a node can be associated with sideinformation. In one embodiment, the node can contain a pointer to ablock of memory with the side information. Alternatively, the node cancontain the name of, or a pointer to, a file stored on a local disk, ora shared network resource, that contains the side information. Inanother embodiment, the node data structure itself could contain spacefor the side information data. In yet another embodiment, the node couldstore, or point to, previously encoded data, such as a webpage or emailmessage, and could generate relevant side information on-the-fly.

In the generalized trie structure shown in FIG. 6, the root node 0 isshown as the top node. The root node 0 could, for example, represent theprotocol or data type, such as HTTP or email messaging. The root node 0defines the starting point for the tree, and for subsequent searches, ortraversals, of the tree. Each node in the HNI can point to a unit ofside information, including compression state information, related tothat node, or only the terminating, or leaf nodes in each path can beassociated with a side information unit. Branching off the root node isa second level of nodes, depicted as nodes 1 and 2. Nodes 1 and 2represent data which is related to, and/or derived from, the root node.For instance, the second level of nodes may represent, depending on thedata type associated with the particular hierarchical node index, twoseparate MIME types for email, or different HTML media types for an HTTPrequest. A third level, as shown by the nodes 1.1, 1.2, 2.1 and 2.2, isdirectly derived from, or related to, the nodes in the second level,namely nodes 1 and 2, and indirectly derived from, or related to, theroot node 0. These third-level nodes could, for example, represent thefirst messages in email threads, or the domain names in URLs associatedwith different webpages. A fourth level of nodes, represented by nodes1.1.1 and 1.1.2, are derived from third-level node 1.1, while nodes1.2.1, 1.2.2 and 1.2.3 are derived from third-level node 1.2. Thesefourth-level nodes could be, for example, the next email messages in theemail threads, or could be, the paths in the URLs. Each new compressionof similar data can create new branches in the tree extending fromprevious nodes.

Exemplary HNIs are shown in FIGS. 6 a and 6 b, which show HNIs grown ordeveloped from HTTP compression and email message compression,respectively. A HNI can be created for each type, or piece, of datapreviously encoded or decoded by the server and mobile device 100,respectively. For example, each of the server and mobile device 100 cancreate and maintain HNIs related to compression and decompression ofHTTP webpages, and can create and maintain other HNIs related tocompression and decompression of email messages. In FIG. 6 a, the rootnode 334 indicates that the HNI maps compression of HTTP webpages. Twonodes 336 and 338 branch from the root node 334, and represent webpagescreated with Hypertext Markup Language (HTML) and JavaScript™ (JS),respectively. The third-level nodes 340, 342 and 366 contain the highlevel domain names CNN.COM:80, RIM.NET:80 and CNN.COM:80, respectively.The domain names are normalized to explicitly add the port numbers. Thislevel could equally contain IP addresses or other network addresses.

Each node in the path from the root node 334 to respective leaf nodesrepresents constituent parts (e.g. protocol; domain name:port; path; andoptionally query) of a Uniform Resource Locator (URL) for an accessedwebpage, plus a unique identifier to uniquely identify the contents ofthe webpage associated with the URL at the time the page was accessed.The unique identifier is required to deal with constantly changingwebpages associated with particular URLs. Thus, the path traversingnodes 334, 336, 340, 344, 346, and 350 represents the URLHTTP://CNN.COM:80/NEWS/WORLD/FR.HTML. Leaf nodes 356 and 358 representthe contents of this URL at two different access times, as indicated bythe different unique identifiers ‘4543ef32’ and ‘32309a31’,respectively, and point to side information created for the webpage atthe respective times. The separate variants of a particular URL,indicated by leaf nodes 356 and 358 can be ordered by, for example,creation date and time. For example, newer variants of a URL can alwaysbe indexed, or added, to the “right” of older variants. Thus, insearching or traversing the HNI, the search algorithm can identify andaccess the side information associated with the newest variant of agiven URL. The unique identifier can be any identifier that uniquelyidentifies the contents, such as a hash of the contents of the accessedpage, at the time the side information is created. Hash schemes that canbe used include CRC-32, MD5, and MD4, or any suitable hashing techniquethat provides a good hash distribution. If the particular hash techniqueimplemented is not sufficient to guarantee uniqueness, the uniqueidentifier can also include other information, such as the size of theside information, in bytes, associated with the accessed data.

Following the path through nodes 334, 336, 344, 348 and 352 leads to theleaf node 360, containing unique identifier ‘874532ed’, for URLHTTP://CNN.COM:80/NEWS/SPORTS/SOCCER.HTML. Similarly, the path throughnodes 334, 336, 344, 348 and 354 represents the URLHTTP://CNN.COM:80/NEWS/SPORTS/HOCKEY.HTML, and leads to two leaf nodes362 and 364, indicated by unique identifiers ‘3432edda’ and ‘9328abcd’,respectively. The path through nodes 334, 366 and 368 represents afurther URL for HTTP://CNN.COM:80 created under JS. The uniqueidentifier ‘48362bb’, shown at node 368, stores the location of the sideinformation associated with the compression of this URL.

FIG. 6 b shows a HNI created for email messages. In contrast to the HTTPexample of FIG. 6 a, in this example of an email HNI, side informationcan be associated with intermediate nodes, as well as leaf nodes. Theroot node 370 indicates that the HNI maps EMAIL side information relatedto email messages. The second-level node 372 indicates that the mediatype of the email messages, which in this case is MIME-version: 1.0. Thethird-level nodes 374 and 376 indicate the content-type of the messages,shown as text/plain and multipart/mixed, respectively. The path throughnodes 370, 372, 374, 378, 380 and 384 depict a thread of email messagesof MIME-version 1.0, context-type: text/plain, starting with a firstmessage, Message 1, a reply to the first message, Reply 1.1, and afurther reply, Reply 1.1.1. Each of nodes 378, 380 and 384 can containside information, including state compression information related tocompression of its respective message or reply. Four other paths areshown in FIG. 6 b. These paths are composed of the nodes 370, 372, 374,378, 382 and 386; nodes 370, 372, 374, 378, 382 and 388; nodes 370, 372,390, 392 and 394; and nodes 370, 372, 390, 392 and 399, respectively,and depict separate email threads. Each of the message nodes 378, 382,386, 388, 390, 392, 394 and 396 can have side information associatedtherewith. This side information can include state compressioninformation derived from the compression of the respective messages andreplies.

When dealing with YK compression or other grammar-based compressiontechniques, the side information includes grammar rules and/or frequencycounts (compression state information) of previously compressed data.Use of compression state information from compression of related datacan improve data compression of new related data, or future nodes. Ifboth parties to a communication have access to compression stateinformation related to previous data compressions, they cansignificantly improve compression and decompression efficiency throughinteractive compression.

FIG. 7 is a flowchart of a method of interactive compression forcommunication between the server and mobile device 100. Sideinformation, including compression state information, that has beenpreviously stored as a result of previous related data compressions isretrieved. The determination, or identification, of the compressionstate information to use in the data compression can be effected byeither the mobile device 100 or the server.

Once a relationship between the mobile communication device 100 and theserver is established, such as by having the device 100 transmit asignal to the server indicating that the device is YK-enabled, and byhaving the server return a Device ID, the mobile device 100 and theserver synchronize their respective side information databases 314 and324 (step 430) in order to implement interactive compression and improvesubsequent data compression. Synchronization of the side informationdatabases 314 and 324 ensures that the mobile device 100 and the serverare aware of, or share, common side information. Typically, thesynchronization will involve a mapping or identification of common sideinformation entries within each database. As used herein, ‘common’denotes information known to both parties to a communication. The commoninformation described herein can be pointers to, or other locators of,side information; the side information itself; and/or copies of theoriginal data, such as webpage data or email messages, from which theside information can be derived. Common information can be stored in acentral location accessible to both parties; or can be separately storedand maintained in parallel by the two communicating entities.Synchronization can occur only when the device 100 and the serverinitially establish communication, periodically, or when new informationis added to either database. One embodiment of a method of synchronizingthe databases is described with reference to FIG. 8, below.

Once the side information databases 314 and 324 are synchronized, anidentification of the data being requested is determined (step 432).Based on the identification of the requested data, common sideinformation, including compression state information, that is relevantor related to the requested data and known to both the server and mobiledevice 100 can then be determined (step 434). If the side information isrepresented or organized in a trie structure, the related common sideinformation can be identified by traversing or searching the tree todetermine common nodes based on the identification of the requesteddata, such as its URL or email message identifier. One method ofdetermining common side information, including compression stateinformation entry(ies), is described in relation to FIG. 9. Theidentification of the common side information can be performed at eitherthe mobile device 100 or the server.

If the common side information identification is being effected at themobile device 100 in step 434, the mobile device 100 transmits a requestfor the data to the server that includes an identification of commonside information determined at step 434, including and identification ofcommon compression state information (step 436). The device 100 thenwaits to receive the requested data, in a compressed format, from theserver (step 438). The compressed data is accompanied by anidentification, or other indication, as to the compression stateinformation used in its compression. Using this compression stateinformation, the device 100 can then decompress the data, through itsdecoder 103, and display, or otherwise provide the decompressed data, tothe user (step 440).

If the server identifies the common side information at step 434, theMDS then retrieves the requested data (step 442). The requested data maybe located within the server, or may be accessible through a remoteserver, such as HTTP server 275, over the network 200. After retrievingthe data, the server compresses the requested data (step 444), throughits encoder 277, using compression state information associated with atleast one unit of common side information identified at step 434. Theserver then transmits the compressed data, together with an indicationor identification of the compression state information used to compressthe data (step 446).

Either the device 100 or the server can replace a unit of sideinformation with a new unit of side information that is similarlyrelated to the data.

In one embodiment, the replacement policy is age-dependent, i.e., sideinformation that exceeds a predetermined age can be replaced by new sideinformation similarly related to the data. For example, if a webpage wasused, at one point in time, as the basis for creating compression stateinformation to be used in later compressions, after a certain duration,the contents of the “same” webpage (the one with the same URL) may havechanged, perhaps to the extent that the compression state information isnow inappropriate for achieving a good compression ratio whencompressing even the same webpage now and in the future. Therefore, thecurrent contents of the same webpage can be used to create new sideinformation to replace the old side information.

In another embodiment, the replacement policy is compression-dependent.If compression of the data with the appropriate side informationavailable achieves at least a predetermined compression ratio, that sideinformation can be retained, However, if the predetermined compressionratio is not achieved using that side information, new side informationsimilarly related to the data can be created to replace the old sideinformation.

In yet another embodiment, the replacement policy is to constantlyupdate side information any time a document is compressed.

FIG. 8 depicts an exemplary method of synchronizing the side informationdatabases 314 and 324. After the communication between the device 100and the server is established, the device 100 can transmit a devicehierarchical node index (such as the one shown in FIG. 6), or portionthereof, to the server (step 450). The device hierarchical node index(HNI) includes a number of nodes, at least some of which index, pointto, or contain side information related to data which has beenpreviously compressed by the server and transmitted to the device 100.The server receives the device HNI (step 452) and compares it to theserver HNI (step 454). The server then determines nodes shared, or incommon, between the device HNI and the server HNI, and creates a sharedHNI that includes the nodes common to the device 100 and the server(step 456). The shared HNI can be determined in many manners. In oneembodiment, the shared HNI can be created by comparing all of the nodesin the respective HNIs, determining all of the nodes common to both nodeindexes and creating a shared hierarchical node index based on thecommon nodes. Alternatively, the shared HNI can be created bydetermining all of the nodes which are in one HNI and not in the other.This shared HNI can be provided to the device 100, if the device 100 isto identify common side information, as described above. Afterdetermining the shared HNI, the device and/or server HNI can be updatedto reflect the differences between the device and the server HNIs. Forinstance, once the shared HNI is determined, the nodes in the device HNIwhich are not listed in the shared HNI can be deleted from the deviceHNI. In another embodiment, the server can request the indexes for thenon-common nodes from the device 100 and update the server HNI and theshared HNI accordingly.

A copy of the shared HNI can be stored in a database, such as the sideinformation databases within the device and the server. Alternatively,the shared HNI can be stored in a central repository, whereby the deviceand the server may access the shared node index to update when required.If the device 100 and the server have previously communicated andexchanged side information database information, the completehierarchical node index need not again be shared between the device 100and the server to effect synchronization in subsequent communicationsessions. For example, if the server recognizes the Device ID sent bythe device 100 at the time of establishing a communication session, thedevice 100 can merely send side information created since its lastinteraction with the server.

Synchronization typically occurs each time the device is initiallyconnected to the server, and can occur periodically as communicationscontinue between the server and the device 100. Ongoing synchronizationcan also be effected in order to maintain the shared HNI on the server,or to maintain shared HNIs on both the server and the device 100. Theindividual device and server HNIs will be updated as communicationbetween the device 100 and the server continue. In order to maintain theshared HNI, the shared HNI can also be periodically or continuouslyupdated. This updating can be performed by synchronizing the HNIs atpredetermined intervals. Maintaining the synchronization between thedevice and the server can also be effected by both the device and theserver providing their rules for the addition or removal of nodes to theother communicating party. In this manner, an update on one of the sideinformation databases is reflected on the other, since they know eachother's management rules. Corresponding updates to the shared HNI canalso be performed. Alternatively, every new node that is added to eitherHNI can be immediately transmitted to the other.

FIG. 9 shows a method of determining common side information, and itsassociated compression state information, to be used for the compressionof requested data. Once the data to be requested is identified, such asby its URL or email thread, the data identifier is parsed into itsrespective elements, such as its constituent protocol, domain name,path, etc., as described above in relation to the HTTP HNI depicted inFIG. 6 a (step 480). Depending on whether the device or the server isdetermining the shared compression state information (see e.g.description of FIG. 7), the appropriate HNI is accessed (step 482). TheHNI is then searched to identify relevant entries within the HNIcontaining side information related to the requested data (step 484). Inone embodiment, this is performed by comparing the parsed dataidentifier elements to the nodes in the HNI. In accordance withpredetermined rules, side information, including compression stateinformation, can then be selected (step 486).

The manner in which side information is selected will now be describedwith reference to the exemplary HNI depicted in FIG. 6 a. Clearly, ifthe search or traversal of the HNI reveals all the constituent parts ofa identifier associated with the requested data in a single path (i.e.an exact hit for a particular URL), such asHTTP://CNN.COM:80/NEWS/WORLD/FR.HTML, the predetermined rules can be setto choose the side information associated with all of the leaf nodes,such as leaf nodes 356 and 358, associated with the URL, or with some,or one, of the leaf nodes, such as leaf node 358. For example, in anembodiment, the rule could be set to choose the side informationassociated with the most recent leaf node. Generally, when the data isHTTP data, the side information, and its associated compression stateinformation, that is ‘closest’ to the lowest common node, and is a leafnode (i.e., has no child nodes), is selected. As will be understood, itis only necessary to choose leaf nodes when the requested data iswebpage, or other data in which a partial path may not point to actualdata. In implementations in which intermediate nodes can contain oridentify side information, and associated compression state information,such as in the HNIs representing email threads in FIG. 6 b, non-leafnodes can also be selected.

Where all the constituent parts are not found in the HNI in a singlepath (i.e. where there is no exact hit in the traversal of the tree),rules based on the ‘closeness’ of the nodes within the HNI can be used.Depending on the desired implementation, and type of data beingcompressed, ‘closeness’ can, for example, be based on minimum number ofmatched elements or common nodes, or on a maximum number of unmatchedelements. ‘Common nodes’ are nodes within a single path that areidentical in content and order to the parsed parts of the identifierbeing searched. For example nodes 340 (CNN.COM:80), 366 (HTML) and 334(HTTP) are common nodes to nodes 344, 346, 348, 350, 352 and 354.However, node 366, which indicates the same domain name (CNN.COM:80) isnot a common node to any of nodes 344, 346, 348, 350, 352 and 354.

In the following examples the identifier of the requested data isHTTP://CNN.COM:80/NEWS/WORLD/CANADA.HTML and the shared HNI is as shownin FIG. 6 a. In a first embodiment, the definition of closenessspecifies a minimum distance between the root node and the closestcommon ancestor between two nodes (i.e. the minimum number of matchednodes or elements). For example, by traversing the tree from the root toa first non-identical node, it can be seen that the requested dataidentifier and nodes 348 (HOCKEY.HTML) and 352 (SOCCER.HTML) share node344 (NEWS) as their closest, or least distant, common ancestor node(other common ancestor nodes are nodes 340, 336, and 334). Node 344 isfour nodes down from the root of the tree (i.e. has a ‘root closeness’of ‘4’). If a closeness rule in an application specifies a minimum rootcloseness of ‘1’, ‘2’, ‘3’, or ‘4’ then the side information associatedwith the leaf node 360 depending from node 352, or leaf nodes 362 and364 depending from node 354, could be used as side information forcompression of the requested data. If the specified root closeness ofthe closest common ancestor node is ‘5’, the side information associatedwith nodes 352 and 354 could not be used. However, the side informationassociated with the leaf nodes 356 and 358 depending from node 350(FR.HTML) could be used, since requested data and the path from the rootnode 334 to node 350 have a common ancestor node 346 that has a rootcloseness of ‘5’. The selection of the required number of matchedelements is a matter of choice, and will depend on the application,protocol and data type.

In a second embodiment, closeness is defined as the maximum number ofunmatched elements between the constituent parts of the requested dataidentifier, and paths within the tree. If we are again looking for sideinformation to use in the compression ofHTTP://CNN.COM:80/NEWS/WORLD/CANADA.HTML, and the maximum number ofunmatched elements is specified as ‘1’, then only the side informationassociated with node 350 (FR.HTML) could be used. If the maximum numberof unmatched elements were increased to ‘2’, the side informationassociated with nodes 350, 352 and 354 could all be used. Again, themaximum number of unmatched elements is a matter of choice and design.

Where the requested data, such as a webpage, includes different types ofcompressible information (e.g. text and video), improved compression canbe achieved by using different compression state information for eachtype of information. In such cases, multiple units of side informationmay need to be identified. Multiple units of side information, and theirassociated compression state information, can also be selected as beingrelevant to a current data request according to predetermined rules. Itis also possible to implement rules to identify multiple related unitsof side information as described above, and to choose among them, or tocompress the data according to each identified unit and select the unitof side information giving the best compression ratio. A combination ofthese methods can also be used, whereby each node is given a particularrelative strength according to its age and level within the hierarchy,and only the side information from those nodes with the highest combinedrating is used.

FIG. 10 shows a method of compressing data when multiple units of sideinformation, associated with multiple compression state informationentries, are identified. After the multiple compression state entriesare identified (step 490), the requested data is then retrieved by theserver (step 492). One of the multiple compression state entries is thenselected (step 494) and then fed through the encoder (step 496),preferably a YK encoder. The encoder is then flushed, to clear itscache, and the output from the compression of the compression stateentry is discarded (step 498). The requested data is then fed throughthe encoder (step 500), which compresses the requested data using theparameters of the compression state entry. The characteristics of thecompression, such as the compression ratio, are then determined (step502). This information can then be stored in a database or kept inmemory (step 504). A check is then performed to determined if therequested data has been compressed using all of the identifiedcompression state information entries (step 506). If not, anotheridentified compression state information entry is selected (step 494)and steps 496 to 504 repeated for the newly selected compression stateinformation entry. After the requested data has been compressed usingall of the compression state information entries, the characteristics ofall of the compressions are compared and the compression stateinformation entry providing the best compression, such as the bestcompression ratio, is determined.

FIG. 11 shows a method of compressing data, such as a webpage,containing multiple data types. After determining the multiplecompression state information entries (step 510) for use in the datacompression, the requested data is then retrieved by the server (step512). In this example, the requested data is assumed to containseparately identifiable components associated with each data type. Theseparate components can be individually identified and parsed by theserver to determine their constituent elements (step 514). Separateunits of side information can then be identified, as described above,for each component (step 515), and each component can then be compressedby the server using the compression state entry identified for thatcomponent (step 516). Alternatively, as described in FIG. 10, eachcomponent may be compressed using multiple compression state informationentries. The compressed data is then transmitted to the device (step518).

In one embodiment, the compressed components are combined to form asingle data stream before being transmitted to the device. This datastream can include a header indicating the compression state entriesused to compress each component, so that the device 100 can decompressthe data stream. Alternatively, the components can be individuallytransmitted to the device with headers indicating the relationshipbetween the individual components. The header preferably includes anindication or identification, of the compression state information used.

In the above description, for purposes of explanation, numerous detailshave been set forth in order to provide a thorough understanding of thepresent invention. However, it will be apparent to one skilled in theart that these specific details are not required in order to practicethe present invention. In other instances, well-known electricalstructures and circuits are shown in block diagram form in order not toobscure the present invention. For example, specific details are notprovided as to whether the embodiments of the invention described hereinare implemented as a software routine, hardware circuit, firmware, or acombination thereof.

Embodiments of the invention may be represented as a software productstored in a machine-readable medium (also referred to as acomputer-readable medium, a processor-readable medium, or a computerusable medium having a computer readable program code embodied therein).The machine-readable medium may be any suitable tangible medium,including magnetic, optical, or electrical storage medium including adiskette, compact disk read only memory (CD-ROM), memory device(volatile or non-volatile), or similar storage mechanism. Themachine-readable medium may contain various sets of instructions, codesequences, configuration information, or other data, which, whenexecuted, cause a processor to perform steps in a method according to anembodiment of the invention. Those of ordinary skill in the art willappreciate that other instructions and operations necessary to implementthe described invention may also be stored on the machine-readablemedium. Software running from the machine readable medium may interfacewith circuitry to perform the described tasks.

The above-described embodiments of the present invention are intended tobe examples only. Alterations, modifications and variations may beeffected to the particular embodiments by those of skill in the artwithout departing from the scope of the invention, which is definedsolely by the claims appended hereto.

What is claimed is:
 1. An interactive compression method comprising:determining, for data to be transmitted, a plurality of compressionstate information entries, each of the plurality of compression stateinformation entries known to communicating parties to a communication,and including parameters of previously compressed data; compressing thedata with each of the plurality of compression state informationentries; determining a one of the plurality of compression stateinformation entries providing a greatest compression ratio; andtransmitting the data, compressed in accordance with the one of theplurality of compression state information entries, from one of thecommunicating parties to an other of the communicating parties.
 2. Themethod of claim 1, wherein the plurality of compression stateinformation entries include at least one of grammar rules and frequencycounts.
 3. The method of claim 1, further comprising transmitting anidentification of the one of the plurality of compression stateinformation entries to the other of the communicating parties.
 4. Themethod of claim 1, further comprising receiving the plurality ofcompression state information entries from the other of thecommunicating parties.
 5. The method of claim 1, wherein determining theplurality of compression state information entries comprises selectingcompression state information entries most recently used incommunications between the communicating parties.
 6. The method of claim1, wherein determining the plurality of compression state informationentries comprises: searching a shared hierarchical node index; andselecting at least two compression state information entries that complywith a predetermined set of rules for determining compression stateinformation entries.
 7. A method of requesting data from a communicatingparty, the method comprising: determining, for data to be received, aplurality of compression state information entries, each of thecompression state information entries known to the communicating party,and including parameters of previously compressed data transmitting adata request, the data request including an identification of theplurality of compression state information entries; and receiving thedata, in a compressed format, with an identification of a one of theplurality of compression state information entries used to compress thedata.
 8. The method of claim 7, wherein the plurality of compressionstate information entries include at least one of grammar rules andfrequency counts.
 9. The method of claim 7, further comprising decodingthe compressed data using the identified shared compression stateinformation entry.
 10. The method of claim 7, wherein determining theplurality of compression state information entries comprises traversinga shared hierarchical node index to identify common entries known tocommunicating parties.
 11. The method of claim 10, wherein thehierarchical node index is stored at a mobile communications device. 12.The method of claim 10, wherein the hierarchical node index is stored ata server.
 13. The method of claim 10, wherein the hierarchical nodeindex is stored in a common shared resource accessible to a mobilecommunications device and to a server.
 14. The method of claim 10,wherein the common entries are represented as nodes in the hierarchicalnode index.
 15. A mobile communication device for use in interactivecompression, comprising: a side information database storing a pluralityof compression state information entries shared between the mobilecommunication device and a server, each of the plurality of compressionstate entries including parameters of previously compressed data for usein interactively compressing the data; an encoder to compress the datawith each of the plurality of compression state information entries; anda processor to determine a one of the plurality of compression stateinformation entries providing a greatest compression ratio, and totransmit the data, compressed in accordance with the one of theplurality of compression state information entries, to the server. 16.The mobile communication device of claim 15, wherein the plurality ofcompression state information entries include at least one of grammarrules and frequency counts.
 17. The mobile communication device of claim15, wherein the side information database stores the plurality ofcompression state information entries in a hierarchical node index. 18.The mobile communication device of claim 15, further comprising adecoder to decompress compressed data received from the server inaccordance with a compression state information entry identified by theserver as a preferred compression state information entry.
 19. A serverfor use in interactive compression, comprising: a side informationdatabase storing a plurality of compression state information entriesshared between the server and a mobile communication device, each of theplurality of compression state entries including parameters ofpreviously compressed data for use in interactively compressing thedata; an encoder to compress the data with each of the plurality ofcompression state information entries; and a processor to determine aone of the plurality of compression state information entries providinga greatest compression ratio, and to transmit the data, compressed inaccordance with the one of the plurality of compression stateinformation entries, to the mobile communication device.
 20. The serverof claim 19, wherein the side information database stores the pluralityof compression state information entries in a hierarchical node index.21. The server of claim 19, further comprising a decoder to decompresscompressed data received from the mobile communication device inaccordance with a compression state information entry identified by themobile communication device as a preferred compression state informationentry.
 22. The server of claim 19, wherein the compression stateinformation comprises at least one of grammar rules and frequencycounts.